1. Field of the Invention
This invention relates to the field of diagnostic assays. More particularly, this invention relates to a peptide-based assay that uses changes in fluorescence polarization to detect serum antibodies to Mycobacterium bovis. 
2. Description of Related Art
Fluorescence polarization is a well-known technique that has been used for a number of applications, including animal disease diagnostics, detection of food-borne pathogens, and grain mycotoxin determination. See M. S. Nasir, M. E. Jolley (1999) “Fluorescence Polarization: An analytical tool for Immunoassay and Drug Discovery.” Combinatorial Chemistry & High Throughput Screening, vol. 2, pp. 177–190. The overall strengths of fluorescence polarization tests lie in the simplicity, ease, rapidity, and cost-effectiveness of the tests protocols. For example, fluorescence polarization tests typically do not require washing steps.
In general, a fluorescence polarization test for disease detection is run as follows. A small quantity of sample is added into a tube containing a buffer solution. A blank is read in the instrument. A fluorescent tracer specific for the disease is added in the same tube and the resultant polarization value is noted within seconds to minutes.
U.S. Pat. No. 6,110,750, which is fully incorporated herein by reference, disclosed a fluorescence polarization technique for detection of animals infected with Mycobacterium bovis. The technique was based on the MPB70 protein secreted by M. bovis. The MPB70 protein was considered to be a highly species-specific immunodominant antigen containing at least three separate M. bovis-specific epitopes. The fluorescence polarization technique used a tracer comprising MPB70 protein conjugated to a fluorophore to detect antibodies to M. bovis in sera from animals, such as cattle, bison, llama, and elk.
However, in order to increase the potential sensitivity of fluorescence polarization assays for M. bovis infection, it is desirable to develop fluorescence tracers based on molecules smaller than MPB70.